10571( 2) - 04/27/05 09:37 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10571 Version: 2 Check-in Date: 27-Apr-2005 13:36:38 1.Proposal Title: The Compact Disk of Blue Stars Orbiting the M31 Black Hole ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO 14 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Tod R. Lauer National Optical Astronomy Observatories, AURA CoI: Dr. John Kormendy University of Texas at Austin N CoI: Prof. Karl Gebhardt University of Texas at Austin N CoI: Prof. Ralf Bender Universitats-Sternwarte Munchen N CoI: Dr. Richard F. Green National Optical Astronomy Observatories, N AURA ------------------------------------------------------------------------------------ 6. Abstract We propose ACS/HRC U and B band imaging of the compact cluster of blue stars at the precise center of M31, which hosts the 1.3X10^8 solar-mass nuclear black hole. Analysis of STIS spectra and WFPC2 images suggest that the cluster is actually a disk. Recovering an accurate light distribution of the disk is essential for obtaining a precise estimate of the black hole mass from the STIS spectra, an approach that is attractive as it bypasses modeling the complex structure and dynamics of the M31 double nucleus by using the Keplerian rotation of the blue disk as a direct mass indicator. Dithered ACS/HRC observations in the blue provide the best spatial resolution available from HST, which is ~2X finer than could be obtained by the WFPC2 observations that first elucidated the structure of the blue cluster. The cluster effective radius (barely resolved by WFPC2) is only ~ 0.06'', thus the ultimate resolution and improved S/N offered by re-observation with ACS/HRC are essential to fully understand the disk inclination and radial starlight distribution. Analysis of the "smoothness" of the blue light distribution may also reveal its composition. The low-luminosity of the disk, M(AB)=-5.5 can be produced by only a few hundred A-stars, a small enough number that fluctuation statistics should leave an obvious signature on the light distribution. ------------------------------------------------------------------------------------ 10571( 2) - 04/27/05 09:37 - [ 2] Observations Description ------------------------ The observations comprise ACS/HRC observations of the M31 nucleus. The first orbit consists of 8 F435W exposures in two groups obtained with 2X2 0.5 pixel dithers to ensure Nyquist sampling. The two groups are offset by 3.5 pixels in X and Y to reject hot pixels and CCD defects. The remaining three orbits consist of 12 F330W exposures, again obtained in three groups with 2X2 0.5 pixel dithers. In this case the three groups are offset by increments of 0.125 pixels in X and Y both for rejection of hot pixels and CCD defects, but also to improve sampling in the ACS/WFC parallel observations. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 10571( 2) - 04/27/05 09:37 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M31NUCLEUS GALAXY, NUCLEUS RA=00H42M44.2300S +/- 0.1", J2000 Mu(V)=13.5 DEC=+41D16'8.81" +/- 0.1" Coordinate Source: HST_IMAGE 10571( 2) - 04/27/05 09:37 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-HRC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.0142 Line_Spacing 0.0124 Coordinate_Frame POS-TARG Pattern_Orient 0.0 Angle_Between_Sides 90.0 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 10571( 2) - 04/27/05 09:37 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 M31NUCLEUS ACS/HRC ACCUM HRC F435W CR-SPLIT=NO 1 298 S PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 M31NUCLEUS ACS/HRC ACCUM HRC F435W CR-SPLIT=NO 1 298 S POS TARG 0.0945, 0.0945; PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 M31NUCLEUS ACS/HRC ACCUM HRC F330W CR-SPLIT=NO 1 672 S PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 M31NUCLEUS ACS/HRC ACCUM HRC F330W CR-SPLIT=NO 1 679 S POS TARG 0, 0.125; PATTERN 1 4 ------------------------------------------------------------------------------------------------------------------------------------ 5 M31NUCLEUS ACS/HRC ACCUM HRC F330W CR-SPLIT=NO 1 679 S POS TARG 0.125, 0.125; PATTERN 1 5 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ M31NUCLEUS 1 ACS/HRC ACCUM HRC F435W 1 none none none 1 N/A M31NUCLEUS 1 ACS/HRC ACCUM HRC F435W 2 none none none 1 N/A M31NUCLEUS 1 ACS/HRC ACCUM HRC F435W 3 none none none 1 N/A M31NUCLEUS 1 ACS/HRC ACCUM HRC F435W 4 none none none 1 N/A M31NUCLEUS 2 ACS/HRC ACCUM HRC F435W 1 none none none 1 N/A M31NUCLEUS 2 ACS/HRC ACCUM HRC F435W 2 none none none 1 N/A M31NUCLEUS 2 ACS/HRC ACCUM HRC F435W 3 none none none 1 N/A M31NUCLEUS 2 ACS/HRC ACCUM HRC F435W 4 none none none 1 N/A M31NUCLEUS 3 ACS/HRC ACCUM HRC F330W 1 none none none 2 N/A M31NUCLEUS 3 ACS/HRC ACCUM HRC F330W 2 none none none 2 N/A M31NUCLEUS 3 ACS/HRC ACCUM HRC F330W 3 none none none 2 N/A M31NUCLEUS 3 ACS/HRC ACCUM HRC F330W 4 none none none 2 N/A M31NUCLEUS 4 ACS/HRC ACCUM HRC F330W 1 none none none 3 N/A M31NUCLEUS 4 ACS/HRC ACCUM HRC F330W 2 none none none 3 N/A M31NUCLEUS 4 ACS/HRC ACCUM HRC F330W 3 none none none 3 N/A M31NUCLEUS 4 ACS/HRC ACCUM HRC F330W 4 none none none 3 N/A M31NUCLEUS 5 ACS/HRC ACCUM HRC F330W 1 none none none 4 N/A M31NUCLEUS 5 ACS/HRC ACCUM HRC F330W 2 none none none 4 N/A M31NUCLEUS 5 ACS/HRC ACCUM HRC F330W 3 none none none 4 N/A M31NUCLEUS 5 ACS/HRC ACCUM HRC F330W 4 none none none 4 N/A 10571( 2) - 04/27/05 09:37 - [ 6] Summary Form for Proposal 10571 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures HRC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/HRC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE PATTERN 1 1 POS TARG 0.0945, 0.0945; PATTERN 1 2 PATTERN 1 3 POS TARG 0, 0.125; PATTERN 1 4 POS TARG 0.125, 0.125; PATTERN 1 5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F435W F330W ------------------------------------------------------------------------------------------------------------------------------------ Target Names M31NUCLEUS ------------------------------------------------------------------------------------------------------------------------------------